Toll-like receptor assays

ABSTRACT

Methods of identifying compounds that modulate the interaction between a TLR and a molecule that interacts with the TLR by direct binding or by inclusion in a complex that associates with the TLR are described. Methods of identifying molecules that interact with a TLR are also described.

CLAIM OF PRIORITY

This application claims priority under 35 USC § 119(e) to U.S.Provisional Patent Application Ser. Nos. 60/530,115, and 60/530,699,both filed on Dec. 16, 2003, the entire contents of which are herebyincorporated by reference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The U.S. Government has certain rights in this invention pursuant toGrant No. GM54060 awarded by the National Institutes of Health.

TECHNICAL FIELD

This invention relates to methods of identifying and using modulators ofToll-like receptors.

BACKGROUND

Effective activation of the immune system in response to a pathogendepends on the ability of antigen presenting cells to deliver thenecessary co-stimulatory (“danger”) signal in the context of antigenpresentation. In mammals, this “adjuvant” effect is the result of thetriggering of a family of germline-encoded receptors (Toll-likereceptors, TLRs), which recognize a variety of conserved microbial andendogenous molecular structures. Activation of different TLRs elicits aproinflammatory response, which promotes the elimination of the pathogenvia the activation of the innate arm of the immune system as well asdetermining the type of adaptive immune response (Th1 versus Th2responses). Skewing between cellular or humoral immune effector functionlargely depends on the nature of the pathogenic insult and therefore onthe specific array of TLRs that is activated.

In rational vaccine design (for example, for infectious diseaseprevention or cancer immunotherapy), manipulation of TLR activation is adesirable approach to developing synthetic immune activators (adjuvants)that can promote an appropriate response (i.e., cellular versushumoral). Conversely, hyperactivation of TLRs may lead to pathologicalsituations in which the blockage of the receptor is desirable, forexample, in some endotoxin-related conditions in which MD-2/TLR4, thesignaling receptor complex for Gram-negative lipopolysaccharide, isactivated.

SUMMARY

The present invention is based, at least in part, on the discovery thatmammalian TLRs, e.g., TLR9 and TLR2, interact directly, e.g., binddirectly to, ligands, e.g., stimulatory pathogen-derived ligands such aslipopolysaccharide (LPS) and CpG DNA. The invention includes methods ofscreening for compounds that can act as TLR ligands, and for compoundsthat can modulate an interaction (e.g., binding) between a TLRpolypeptide and a TLR ligand. Such compounds, referred to herein as “TLRinteractors,” can increase or decrease the interaction (e.g., binding)between a TLR and a TLR ligand. In general, such compounds can modulateTLR signaling, e.g., in a cell that has been activated for suchsignaling (e.g., by contacting the cell with a TLR ligand). Thesecompounds can be used to modulate immune responses to pathogens.

Accordingly, the invention relates to methods of identifying Toll-likereceptor (TLR) interactors. The methods include providing a samplecomprising a TLR polypeptide; contacting the sample with a biotinylatedtest compound, thereby providing a test mixture; incubating the testmixture with a particle comprising a molecule that binds to biotin,e.g., a particle comprising avidin, streptavidin or NeutrAvidin™ (adeglycosylated form of avidin), e.g., a bead, under conditions and for atime sufficient to permit binding between the biotinylated test compoundand the particle, thereby providing a bound particle; isolating thebound particle; and determining if the bound particle is associated withthe TLR polypeptide. A bound particle that is associated with the TLRpolypeptide indicates that the test compound is a Toll-like receptor(TLR) interactor. In some cases, the sample is a biological sample. Thetest mixture can include at, least two different TLRs, which may or maynot interact with each other.

The invention also relates to methods of identifying compounds thatmodulate the interaction between a Toll-like receptor (TLR) and itscognate TLR ligand. The methods include providing a sample comprising aTLR polypeptide; contacting the sample with a cognate TLR ligand and atest compound (consecutively, in either order, or simultaneously),thereby forming a test sample; incubating the test sample for a time andunder conditions sufficient for the TLR ligand to bind to the TLRpolypeptide in the absence of the test compound; and determining bindingbetween the TLR polypeptide and the TLR ligand in the test sample,wherein a difference binding in the test sample compared to a controlindicates that the test compound is a candidate compound for modulatingTLR signaling. In some embodiments, the difference in binding is one ormore of: a difference in a rate of binding; a rate of dissociation; adifference in an amount of binding; or a difference in an affinity ofbinding.

The method of claim 21, further comprising formulating a therapeuticcomposition comprising a candidate therapeutic compound and apharmaceutically acceptable carrier.

In some embodiments, the TLR ligand or TLR polypeptide is biotinylated.In some embodiments, the TLR polypeptide is a chimeric polypeptidecomprising a TLR protein or fragment thereof and a second protein, e.g.,an Fc fragment, or a fluorescent protein, e.g., Green fluorescentprotein (GFP) or a fluorescent variant thereof.

In some embodiments, the TLR ligand or TLR polypeptide is bound to asolid surface; e.g., either the TLR ligand or the TLR polypeptide isbiotinylated and the solid surface comprises avidin, streptavidin, orNeutrAvidin™, a deglycosylated form of avidin.

In some embodiments, one or more of the TLR polypeptide and the TLRligand is labeled, e.g., with a compound that is detectable with timeresolved fluorimetry, e.g., a europium compound or an allophycocyanincompound.

In some embodiments, binding between the TLR polypeptide and the TLRligand is detected using an antibody that specifically binds to the TLRpolypeptide. In some embodiments, the TLR polypeptide is a chimericpolypeptide, and the antibody binds to the second protein in thechimeric polypeptide.

In some embodiments, the TLR polypeptide and TLR ligand are in solution.In some embodiments, time-resolved fluorimetry is used to detect thebinding.

In some embodiments, the TLR polypeptide or TLR ligand is bound to anisolatable substrate, e.g., a bead.

In some embodiments, the TLR polypeptide is a TLR1, TLR2, TLR3, TLR4,TLR5, TLR6, TLR7, TLR8, TLR9, or TLR10 polypeptide. In some embodiments,the TLR polypeptide is TLR2 or TLR9.

In some embodiments, the methods further include determining whether thetest compound modulates TLR9-mediated signaling. A test compound thathas been screened by a method described herein and determined tomodulate TLR9 signaling, can be considered a candidate compound. Acandidate compound that has been screened, e.g., in an in vivo model ofa disorder, e.g., a disorder associated with TLR9 signalling, e.g.,inflammation, autoimmune disorders, and pathogen infection, anddetermined to have a desirable effect on the disorder, e.g., on one ormore symptoms of the disorder, can be considered a candidate therapeuticagent. Candidate therapeutic agents, once screened in a clinicalsetting, are therapeutic agents. Candidate therapeutic agents andtherapeutic agents can be optionally optimized and/or derivatized, andformulated with physiologically acceptable excipients to formpharmaceutical compositions. The invention also relates to compoundsthat modulate TLR9 signalling, identified by a method described herein,and therapeutic compositions containing the compounds, as well asmethods of treating disorders associated with TLR9 signalling byadministering the compounds. Methods of preparing and administering suchcompounds are known in the art.

Thus, the invention includes methods of administering a compound thatmodulates Toll-like receptor (TLR) signaling, identified by a methoddescribed herein, to an animal model of a disorder associated with TLRsignalling; and evaluating an effect of the compound on a parameter ofthe disorder in the animal, e.g., a symptom or other clinical parameter,e.g., morbidity, mortality, or time of onset. A positive effect of thecompound indicates that the compound is a candidate therapeutic compoundfor the treatment of the disorder. The candidate therapeutic compoundcan be optimized, and formulated with a pharmaceutically acceptablecarrier to make a therapeutic composition for the treatment of thedisorder.

As used herein, a “TLR polypeptide” can include a full-length TLRpolypeptide or a suitable fragment thereof, as described herein. In someembodiments, the TLR polypeptide is a chimeric protein, e.g., a peptideincludes a second protein (e.g., a fluorescent polypeptide, a tag, or anFc region of an antibody) expressed in frame with the TLR as a singlemolecule. The TLR ligand or TLR polypeptide can be bound to a solidsurface (in one example, the TLR ligand is biotinylated and the solidsurface comprises avidin, streptavidin, or NeutrAvidin™, adeglycosylated form of avidin). In another embodiment, the TLR ligandand/or TLR polypeptide is labeled, e.g., with a lanthanide chelatefluorophore, and time-resolved fluorimetry is used to detect thebinding. In some embodiments, an antibody that specifically binds to theTLR polypeptide is used to detect binding between a TLR polypeptide anda TLR ligand; for example, an antibody that specifically binds to achimeric TLR protein (e.g., to the non-TLR portion of the chimera) canbe used to detect binding between the TLR polypeptide and TLR ligand.The antibody can be labeled, e.g., with a lanthanide chelatefluorophore, and time-resolved fluorimetry is used to detect thebinding. The method can also be performed such that the TLR polypeptideand TLR ligand are in solution. In another embodiment, the TLRpolypeptide and/or the TLR ligand is bound to a collectable substrate,e.g., a bead.

By “specifically binds” is meant a molecule that binds to a particularentity in a sample, e.g., a specific TLR protein, but which does notsubstantially recognize or bind to other molecules in the sample, e.g.,another type of TLR polypeptide or a non-TLR protein.

“Polypeptide” means a chain of amino acids regardless of length orpost-translational modifications, and thus includes proteins andpeptides.

A “TLR-interactor” is a molecule (e.g., an organic or inorganic smallmolecule, peptide, polypeptide, or nucleic acid) that associates with,e.g., binds directly or indirectly to or forms a complex with, a TLRpolypeptide, e.g., in a cell. TLR-interactors include molecules thatco-immunoprecipitate with a specific TLR polypeptide, as well asmolecules that specifically bind to the TLR polypeptide. TLR interactorscan be of cellular origin or exogenously added, includingnaturally-occurring molecules and synthetic molecules. TLR interactorsinclude TLR ligands and molecules that interfere with binding of a TLRpolypeptide and TLR ligand, e.g., a naturally occurring TLR ligand suchas a pathogen-derived ligand or analog thereof. Such molecules can beidentified using methods described herein.

A “TLR ligand” is a molecule that interacts with a TLR by binding to theTLR, i.e., there is a direct association with the TLR. A “cognate” TLRligand is a natural or artificial ligand that can bind to and activatesignaling through a particular TLR or TLRs. For example, CpG-DNA is anexample of a cognate ligand for, e.g., TLR7, TLR8, or TLR9. LPS is anexample of a cognate ligand for TLR2. In general, the binding of a TLRpolypeptide and a TLR ligand is non-covalent in nature. In someembodiments, a TLR ligand can activate or inhibit signaling through theTLR.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entirety. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

Other features and advantages of the invention will be apparent from thedetailed description, drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic drawing of a ligand binding assay in whichbiotinylated ligand (biotinylated oligodeoxynucleotide; biotinylatedODN) is immobilized on NeutrAvidin™-coated microtiter plates. TLR-GreenFluorescent Protein (TLR^(GFP)) is bound to the biotinylated ligand andbound TLR is detected with an anti-GFP monoclonal antibody, which isdetected using anti-mouse antibody conjugated to horseradish peroxidase(anti-mouse HRP) after a color reaction to detect peroxidase activity.

FIG. 1B is a schematic drawing of a ligand binding assay in whichimmobilized anti-GFP antibody (anti-GFP) captures TLR^(GFP) (e.g., froma cellular lysate) and biotinylated ligand (biotinylated ODN) is boundto streptavidin conjugated to HRP after a color reaction to detectperoxidase activity.

FIG. 1C is a schematic drawing of a ligand binding assay in whichbiotinylated ligand (biotinylated ODN) is immobilized onNeutrAvidin™-coated microtiter plates. TLR^(GFP) is bound to thebiotinylated ligand and bound TLR is detected with an anti-GFPmonoclonal antibody that is also tagged with europium, which is detectedusing an acceptor in an assay to detect time resolved fluorescence(TR-fluorescence).

FIG. 1D is a schematic drawing of ligand binding assays in whichimmobilized anti-GFP antibody (anti-GFP) captures TLR^(GFP) (e.g., froma cellular lysate) and biotinylated ligand (biotinylated ODN), whichbinds to streptavidin that is tagged with europium, which is detectedusing an acceptor in an assay to detect TR-fluorescence.

FIG. 2 is a schematic drawing depicting the principle of the homogenousligand binding assay employing TR-fluorescent resonance energy transfer(e.g., LANCE™ technology). EU is europium, FRET is fluorescenceresonance energy transfer, and APC is allophycocyanin.

FIG. 3A is a bar graph that depicts the results of experiments in whicha solid phase assay was used to detect TLR4^(YFP) or TLR9^(YFP) bindingto immobilized CpG-DNA or control (PBS). Bound TLR was detected with GFPantibody and HRP-conjugated mouse monoclonal antibody followed by acolor reaction to detect HRP activity. Absorbance at 450 nm wasdetected.

FIG. 3B is a bar graph that depicts the results of experiments in whicha solid phase assay was used to detect TLR4^(YFP) or TLR9^(YFP) bindingto anti-GFP coated onto microtiter plates or control (PBS). Bound TLRwas incubated with biotinylated ligand (CpG-DNA). The bound ligand wasdetected with HRP-conjugated streptavidin followed by a color reactionto detect HRP activity. Absorbance of the color obtained after addingHRP substrate was read at 450 nm.

FIG. 4 is a graph illustrating the results of experiments in whichincreasing amounts of biotinylated CpG-DNA (2006) were coated ontomicrotiter plates. Cellular lysates containing TLR9-Yellow FluorescentProtein (TLR9^(YFP)) were incubated then detected by binding to anti-GFPmonoclonal GFP and anti-mouse-HRP followed by a color reaction to detectHRP activity. Absorbance was measured at 450 nm. The results areexpressed as the percent of half-maximal binding.

FIGS. 5A-D are graphs depicting the results of experiments showing thepercent TLR9 binding activity to CpG-2006 immobilized on plates in thepresence of different concentrations of various compounds in solution;R848, E. coli DNA, CpG-DNA 1668, and CpG-DNA 2006.

FIG. 6A is a schematic illustration of the principle behind theAlphaScreen™ assay.

FIG. 6B is a line graph showing the results of an AlphaScreen™ assay ofthe interaction of TLR9-Fc with CpG-DNA (2006 PTO filled squares) andGpC-DNA (2006 GC PTO, open squares).

FIGS. 7A and 7B are bar graphs illustrating the levels of NFκBactivation in HEK 293 cells stably expressing either TLR4 and MD-2 (FIG.7A) or TLR2 (FIG. 7B) after stimulation with PorinB in doses of 0.01μg/ml (lightest gray bars), 0.1 μg/ml (medium gray bars), 1 μg/ml (darkgray bars), or 10 μg/ml (black bars).

FIG. 7C is a Western blot showing levels of biotinylated PorinB, probedwith an anti-biotin antibody (α-biotin), demonstrating the purity of thepreparation.

FIG. 7D is a Western blot showing levels of binding of PorinB tocell-surface TLR2^(GFP) fusion constructs, detected using an anti-GFPantibody, at 0, 1, 2, and 3 hours after stimulation with biotinylatedPorinB.

FIG. 8A is a line graph showing the binding of different concentrationsof plated ligands to a TLR2:Fc fusion protein.

FIG. 8B is a line graph showing that increasing concentrations of Porinor bacterial alkaline phosphatase (BAP), bind to TLR2:Fc (filleddiamonds), but not to TLR4:Fc (filled squares).

FIG. 9 is a pair of Western blots showing the effect of increasingconcentrations of B1287, an LPS antagonist, on binding of biotinylatedLPS to cell-surface TLR4 (top panel) and soluble MD-2 (bottom panel).

DETAILED DESCRIPTION

Toll-like receptors (TLRs) are molecules that can act as mediators ofimmune system responses and of related physiological phenomena such asinflammation. TLRs manifest their effects as part of a signaling pathwaythat leads to the expression and activation of molecules that ultimatelyinduce, e.g., immune system activation. Accordingly, identification ofmolecules involved in TLR signaling pathways is useful for identifyingtargets for drugs that affect immune system activation and relatedeffects. The identification of compounds that disrupt or enhance theinteraction between TLR polypeptides and their cognate ligands oranalogs thereof (e.g., molecules that are known to be capable ofinteracting with the TLR and can elicit at least one activity associatedwith signaling by that TLR, e.g., analogs of naturally-occurringligands) is useful for identifying compounds that modulate the effectsof TLR signaling, for example by reducing inflammation or decreasing orenhancing an immune response. Because of the importance of TLRs inimmune response signaling, fast and inexpensive strategies foridentifying compounds that are able to interact with TLRs are ofcommercial and practical use.

Several different approaches for screening assays suitable for theidentification of TLR modulators that interact with TLRs (TLRinteractors) are described herein. TLR interactors include moleculesthat directly bind to a TLR polypeptide (e.g., TLR ligands) or areassociated with a TLR polypeptide in a complex that includes otherproteins. The assays can be adapted to identify compounds that candisrupt the interaction between a TLR polypeptide and its cognateligand.

Screening Assays

In general, the invention provides methods (also referred to as“screening assays”) for identifying compounds that can modulate TLRsignaling. Such compounds are candidate compounds (e.g., proteins,peptides, peptidomimetics, peptoids, small non-nucleic acid molecules,nucleic acids, synthetic nucleic acids, or other drugs) for thetreatment of disorders associated with TLR signaling. The compounds canbe, e.g., naturally occurring interactors (e.g., bacterial DNA) orsynthetic molecules such as an engineered CpG-DNA. In general, thecompounds will be agonists or antagonists of the interaction between aTLR polypeptide and its cognate TLR ligand. For example, some compoundsmay have competitive or non-competitive action for TLR ligands.

A number of methods are known in the art for determining the effect of atest compound on ligand/receptor interactions. For example, threecommonly used experimental protocols to determined binding include:

(1) Saturation binding experiments. The extent of binding is measured inthe presence of different concentrations of the a ligand. From ananalysis of the relationship between binding and ligand concentration,the number of binding sites, B_(max), and ligand affinity, K_(D), can bedetermined.

(2) Kinetic experiments. In these experiments, saturation andcompetition experiments are allowed to incubate until binding hasreached equilibrium. Kinetic experiments measure the time course ofbinding and dissociation to determine the rate constants for ligandbinding and dissociation. Together, these values can be used tocalculate K_(D).

(3) Competitive binding experiments. The binding of a singleconcentration of ligand is measured in the presence of variousconcentrations of an unlabeled competitor. The data can be used todetermine the affinity of the receptor for the competitor.

All of these methods are known in the art. See, e.g., Clegg, ProteinTargeting Protocols (Methods in Molecular Biology, Vol 88), Humana Press(1998).

Compounds identified by a method described herein can have a stimulatoryor inhibitory effect on the activity of a TLR, for example bystimulating or inhibiting TLR-mediated signaling (TLR signaling). Forexample, a compound may have a stimulatory or inhibitory effect on anactivity of a TLR ligand, including the ability of the TLR ligand tostimulate TLR-mediated signaling. Thus, compounds identified using themethods described herein can be used to modulate the activity ofTLR-mediated signaling. For example, a compound that increases theinteraction between a TLR polypeptide and its cognate TLR ligand isuseful for activating the immune system in a therapeutic or prophylacticprotocol, or to elaborate a biological function of a TLR polypeptide anda TLR interactor, e.g., to identify new pathways for potentialtherapeutic modulation, e.g., new therapeutic targets. A compound thatdisrupts an interaction between a TLR polypeptide and a TLR interactor,e.g., a ligand, can be useful for decreasing an immune-mediated responsesuch as an undesirable inflammatory response.

Determining the ability of a test compound to modulate TLR activity canbe accomplished by monitoring, for example, any suitable aspect ofsignaling mediated by the particular TLR polypeptide, includingactivation of the immune system of a subject, e.g., a mammal, e.g., anexperimental animal or a human, or activation of a cellular pathwayassociated with immune activation. Suitable methods include, but are notlimited to, detecting cellular activation of TLR-expressing cells bymeasuring cytokine or chemokine responses, detection of surfaceupregulation of inducible genes (such as CD80, CD86, CD40, MHCII, orCD54), measuring the expression, activity, or translocation ofDNA-binding or nuclear transcription factors (e.g., NF-κB), Northernblotting to detect the synthesis of immunologically relevant genes,RT-PCR or real-time PCR assays to detect upregulation of RNA encodingimmunologically relevant genes (including genes of the signaling pathwayactivated by the TLR polypeptide, e.g., TNF-alpha, IFN-alpha, IL-6,IL-1, IL-8 and RANTES), activation of IL-10-producing regulatory T cellsin response to TLR activation (e.g., van der Kleij et al., 2002, J.Biol. Chem., 277:48122-48129), detection of dendritic cell maturation asa readout of immune stimulation, or detection of B cell proliferation inresponse to ligand stimulation. Methods of detecting such activities areknown in the art. In cell-based or cell-extract assays, the cell can be,for example, of mammalian origin, e.g., human, murine, rabbit, hamster,monkey, or rat. In general the cell is one that either naturallyexpresses the TLR polypeptide of interest or the cell is geneticallyengineered to express the TLR polypeptide of interest. Generally, uponstimulation with the appropriate molecule (e.g., a CpG-DNA forstimulation of TLR9 signaling), the cell is also capable of carrying outone or more activities in the signaling pathway of the TLR polypeptideof interest.

Toll-like Receptor Ligand Binding Assays

In general, the new assays described herein for identifying compoundsthat interfere with the interaction between a TLR polypeptide and TLRligand involve a known TLR cognate ligand that can bind to the TLRpolypeptide used in the assay (e.g., any of TLRs 1, 2, 3, 4, 5, 6, 7, 8,9 and/or 10), to a complex of a TLR polypeptide and an associatedmolecule (e.g., TLR4 and MD-2), or to a homo- or heteromultimericcomplex of two or more TLRs (e.g., TLR2/TLR1 or TLR2/TLR6heteromultimers). In some embodiments, the TLR ligand and/or TLRpolypeptide is labeled. A test compound (e.g., a potential receptoragonist or antagonist) is included in a test sample and is examined forits ability to compete for the TLR ligand interaction with the TLRpolypeptide. Because only the known ligand is labeled, a decrease in theamount of measured label indicates that the test compound interactedwith the receptor or interacted with the ligand in a manner thatinhibits interaction of the ligand with the TLR polypeptide. A testcompound can also increase the binding of a TLR ligand, thereby loweringthe K_(d) for a ligand to the respective TLR polypeptide.

Assays for identifying compounds that interact with, e.g., bind directlyor indirectly to or form complexes with, a TLR polypeptide are alsodescribed herein. Such assays generally involve labeling potential TLRinteractors and contacting the TLR polypeptide with the labeledinteractor(s) as described below. Molecules that are associated with theTLR polypeptide can then be identified using methods known to those inthe art, including electrophoresis and sequencing.

In some assays, TLR interactors are identified, for example, byconducting an assay described herein in the presence of a biologicalsample suspected of containing a TLR interactor or in the presence of amixture of library of molecules suspected of containing a compound thatcan interact with a TLR polypeptide. After a molecule is identified asinteracting with a TLR polypeptide, characteristics of the TLRinteractor can be determined. Such characteristics include, but are notlimited to, the chemical nature of the interactor (e.g., a nucleic acid,a polypeptide, a small non-nucleic acid organic compound, or a smallinorganic compound), the molecular weight of the compound, the charge ofthe compound (e.g., at physiological pH), and the ability of thecompound to induce or inhibit activation of the cognate TLR polypeptideto with which it can interact). Methods known in the art can be used tooptimize the interactor, e.g., to increase efficacy, binding, or otherdesirable attributes.

Precipitation Assays

One method of identifying compounds that modulate an interaction (e.g.,binding) between a TLR polypeptide and a TLR ligand is a precipitationassay. In general, the TLR ligand (e.g., CpG-DNA or lipopolysaccharide(LPS)) is labeled using methods known in the art. interaction (e.g., bydecreasing the Kd). An embodiment of the precipitation is described inthe Examples (infra).

The precipitated material can also be subjected to further analysis toidentify TLR interactors in the precipitate. For example, proteins inthe precipitate can be separated by electrophoresis and proteins inbands can be sequenced. Molecules identified in this assay can serve astargets for compounds that affect TLR-mediated signaling and affectimmune system activation and inflammation.

Assays will typically be carried out in vitro, e.g., using a celllysate, or a cell fraction that contains a suitably labeled TLRpolypeptide.

The assay described above can be modified for use with a ligand that islabeled with any entity that can be bound by a second entity that isbound to a bead or other collectable substrate. Collectable substratescan include substrates that are collectable by, e.g., centrifugation,floating, settling, magnetism, or filtration. For example, the ligandcan be labeled with a tag that can be detected using immunocytochemicalmethods. In this case, the appropriate second entity that binds the tagis attached to the substrate and the assay carried out substantially asdiscussed above.

This type of assay, in which the ligand is labeled and detected,provides advantages over methods in which only the TLR polypeptide islabeled. For example, using this method, it is possible to determine thekinetics of the interaction between the TLR polypeptide and the TLRligand. Also, it can be easier to label the ligand than to engineer alabeled, functional TLR polypeptide.

In some embodiments, the method is an assay that can be used to identifynovel candidate TLR interactors, e.g., ligands. For example, a sample(e.g., a cell or cell lysate) containing a labeled (e.g., bybiotinylation) test compound, e.g., a potential TLR ligand, is incubatedwith the TLR polypeptide. After incubation under conditions and for aperiod of time sufficient to permit association of the TLR polypeptideand a TLR ligand (at least about 1 minute, e.g., 5 minutes, 10 minutes,15 minutes, 30 minutes, 1 hour, 2 hours, 5 hours, 8 hours, 16 hours, or24 hours), the labeled test compound is precipitated, e.g., abiotinylated test compound (and any molecules bound to or complexed withit) is precipitated using streptavidin-coated beads. The precipitatedmaterial is transferred to a membrane and visualized on Western blots;test compounds that precipitate TLR polypeptide are candidate TLRinteractors.

For example, the TLR ligand can be biotinylated using methods known inthe art, and incubated with a cell expressing the cognate TLRpolypeptide. In some embodiments, after incubation under conditions andfor a period of time sufficient to permit association of the TLRpolypeptide and ligand (at least about 1 minute, e.g., 5 minutes, 10minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, 5 hours, 8 hours, 16hours, or 24 hours), the cells are lysed and the biotinylated ligand isprecipitated, e.g., using a collectable substrate that can bind tobiotin, such as streptavidin-coated beads. Other biotin-binding entitiescan be used, e.g., avidin or NeutrAvidin™, a deglycosylated form ofavidin. The precipitated material is electrophoresed, transferred tomembranes and visualized on Western blots. Alternatively, TLRpolypeptide/ligand interaction can be determined by incubating cellularlysates with labeled ligand and TLR polypeptide/ligand interaction isdetected similarly. In some embodiments, instead of a biotin label, adifferent small molecule label such as digoxin is used. The collectablesubstrate is coated with a suitable molecule (e.g., an antibody orantibody fragment) that can bind to the small molecule label.

The amount of TLR polypeptide bound to the biotinylated ligand can bequantitated using methods known in the art. For example, if a TLR fusionprotein (e.g., composed of a TLR polypeptide and a fluorescent protein),is used as the TLR polypeptide, the fluorescent protein can be detectedusing methods known in the art, e.g., by direct detection of thefluorescent protein, or in a sandwich assay in which an antibody thatspecifically binds to the fusion protein (e.g., to the fluorescentprotein part of the fusion protein) is added to the precipitate and theantibody detected using a second antibody that specifically binds to thefirst antibody and is also conjugated to a detectable label such ashorseradish peroxidase (HRP). This precipitation assay can provide acontrol or reference for assays testing the ability of a test compoundto modulate the interaction between the TLR polypeptide and its ligand.In such assays, a test compound is included in the incubation mixtureand the amount of interaction between the TLR polypeptide and ligandassayed. A comparison between the control and the sample containing thetest compound is made (e.g., by assaying the amount of signal on theWestern blot). A decrease in the amount of interaction in the presenceof the test compound compared to the amount of interaction in theabsence of the test compound indicates that the test compound decreasesthe interaction. Conversely, an increase in the amount of interactionbetween the TLR polypeptide and ligand in the presence of the testcompound indicates that the test compound increases the

Solid Phase Assays

The use of solid phase binding assays has certain advantages over aligand-precipitation approach. Depending on the experimental setup for asolid phase assay, either the ligand or the TLR polypeptide isimmobilized, e.g., on microtiter plates, and binding of the receptor orthe ligand to the immobilized entity is detected and measured. Handlingof reagents can be automated and small volumes can be used to limit theamounts of reagents necessary to carry out the assay. Since multiplemicrotiter plates can be used in these assays, a large number ofcompounds can be tested simultaneously. Thus, this type of assay isuseful for high-throughput drug screening purposes in which handling ina plate environment and a relatively large number of samples isadvantageous.

FIGS. 1A-1D illustrate the general design of four exemplary solid phasereceptor ligand assays. There are two general types of setups (ligandcoating or receptor coating) and two types of detection systemsdescribed although other detection systems known in the art can be used.The first detection system employs enzyme-linked immunosorbent assay(ELISA) technology for detection and the second type of detection systemuses a fluorescence-based detection technology.

In one example of a solid phase assay, biotinylated ligand (e.g.,biotin-CpG-DNA) is immobilized on a microtiter plate that is coated witha molecule that binds biotin, e.g., avidin, NeutrAvidin™, streptavidin,or an anti-biotin antibody. The TLR polypeptide of interest is labeledand is incubated in the prepared plates. The TLR polypeptide can bepurified, partially purified, or presented in a cell lysate. In general,the TLR polypeptide is labeled by virtue of it being a fusion protein,e.g., a TLR polypeptide with a fluorescent protein such as YFP, GFP, RedFluorescent Protein (RFP) or CFP (Cyan Fluorescent Protein). Methods ofmaking such fusion proteins and stable cell lines that produce suchfusion proteins are known in the art (e.g., Latz et al., 2002, J. Biol.Chem. 277:47834-47843). TLR polypeptide bound to the immobilized ligandcan be detected using a sandwich method. A primary antibody thatspecifically binds to the labeled TLR polypeptide (e.g., an antibodythat binds to the fluorescent protein portion of the TLR fusion protein)is added to the plate, incubated, washed, and then a secondary antibodythat can specifically bind to the primary anti-labeled TLR antibody,e.g., a secondary antibody that is conjugated to a detectable label, isapplied. The detectable label can be enzymatic, e.g., horseradishperoxidase (HRP) or some other detectable label. FIG. 1A illustrates anassay of this type. Variations of this method can be used, such as thedirect use of conjugated primary antibody or ProteinA/G-conjugated toHRP as secondary reagents, or secondary reagents conjugated withdifferent enzymes (such as alkaline phosphatase) or fluorophores (suchas Alexa™ 488).

FIG. 1B illustrates an inverse assay in which the receptor (TLR) iscaptured on the plate via its tag (e.g., anti-GFP). Bound labeled, e.g.,biotinylated, ligand can be detected, e.g., by the use of HRP-conjugatedstreptavidin in an enzyme-linked immunosorbant assay (ELISA). In bothcases, a color reaction is obtained after adding substrate for theenzyme HRP. The receptor/ligand interaction is quantifiable by readingabsorbance in a plate reader.

Other methods of detection can be used in solid phase assays. Forexample, time-resolved fluorescence (TR fluorescence) methods can beused. These methods use lanthanide chelate fluorophores. This methodprovides enhanced sensitivity and increased measurement range overstandard ELISA methods. Time-resolved fluorimetry is possible when afluorescent dye has a long decay time. This allows the measurement ofemission after a time lag (up to 1 millisecond) when non-specificfluorescence from the sample and potential drug or microtiter plate hasdecayed. The elimination of interfering background contributes to highersensitivity compared to methods using conventional fluorophores such asfluorescein and rhodamine. This assay is versatile in drug screening,since background fluorescence of the tested drug can be eliminated as aconfounding factor due to the favorable fluorescence characteristics ofthe lanthanide chelate fluorophores.

A solid phase assay using lanthanide chelate fluorophores is similar tothe ELISA-based assay described above. The steps of this assay involvethe binding of receptor (FIG. 1C) or ligand (FIG. 1D) to the plate,incubating the immobilized entity with ligand or receptor and detectingthe receptor-ligand interaction with europium-labeled detection reagent(e.g., europium-anti-GFP or europium-streptavidin). Such reagents arecommercially available or can be prepared using commercially availablekits (for example, DELFIA® products, PerkinElmer, Boston, Mass.). Oncethe europium-labeled reagents are bound, an enhancement step is appliedto develop the fluorescence, which is then measured.

Homogeneous Assay

An alternative to the precipitation assay and the solid-phase ligandbinding assays is a homogenous assay that has the advantage of furtherreduction of incubation times and wash steps. The homogeneous assayprovides advantages in that it does not require washing steps, thusgreatly simplifying the handling of the samples as compared to theprecipitation and plate assay methods. In homogenous assays, all of theassay components remain in the same liquid phase. Homogeneous assaysparticularly benefit from the use of time-resolved fluorometry (TRfluorimetry) because the sample constituents present during detectioncan cause high background fluorescence when conventional fluorochromesare used.

Generally, in homogenous assays, the test compounds that are assayed fortheir ability to interact with a specified TLR polypeptide are combinedin a sample mixture along with detection reagents. For example, whentime-resolved (TR) fluorimetry is used (described in greater detailbelow), the TLR polypeptide is labeled with a fluorochrome suitable foruse in TR fluorimetry. The detection reagents include an antibody, whichcan specifically bind the TLR polypeptide, labeled with the donorfluorochrome and a ligand bearing an acceptor fluorochrome that iscompatible for use with the TLR polypeptide-associated fluorochrome inTR fluorimetry. Since the method is based on the detection of thefluorescence emitted only when the donor and the acceptor are in closeproximity (e.g., by fluorescent resonance energy transfer (FRET)), freeexcess unbound reagents (e.g., those not in close proximity) do notcontribute to the detected emitted light. Therefore, there is no need towash out excess reagents.

In some embodiments, a test compound is assayed for its ability toenhance or decrease the interaction (e.g., binding) between a TLRpolypeptide and one of its known ligands. In this case, the testcompound is added to the incubation mixture containing the labeled TLRpolypeptide and labeled TLR ligand. The amount of interaction betweenthe TLR polypeptide and its ligand is measured in the presence andabsence of the test compound. A decrease in the amount of interaction inthe presence of the test compound indicates that the test compounddecreases the interaction between the TLR polypeptide and its ligand andthus is a candidate compound for decreasing signaling by that TLRpolypeptide. An increase in the amount of interaction between the TLRpolypeptide and its interactor in the presence of the test compoundindicates that the test compound is a candidate compound for increasingsignaling by the TLR polypeptide. In some cases, compounds that disruptthe interaction between a TLR polypeptide and TLR ligand are furtherassayed for their ability to activate TLR signaling (i.e., to determinewhether the compound is an agonist or antagonist of TLR signaling).

TR Fluorimetry

A sensitive and reliable labeling and detection system is based onTR-fluorimetry. As described herein, the method uses lanthanide chelateswhich give intense and long-lived fluorescence emission (greater than1,000 μs), thereby enabling the measurement of fluorescence emissionsignificantly later than excitation.

TR fluorimetry can be used to assay molecules in the assays describedherein. As discussed above, this method employs TR-FRET (time-resolvedFRET) methodology (FIG. 2), based on labeling using lanthanidechelation. Lanthanide probes are used and their fluorescence lifetimesare assayed using a time-resolved fluorimeter. Lanthanide fluorophorescan increase the sensitivity of an assay since the lanthanidefluorophores have a relatively long life span. Therefore, emissions canbe measured after background fluorescence (e.g., from buffers andmicrotiter plates) has faded. In addition, different lanthanide probesexhibit a characteristic emission peak at specific wavelengths, whichenhances the sensitivity of assays performed with this system. Since thepeaks can be distinguished from one another, assays can be performedusing more than one label. For example, a cell that stably expresses twodifferent TLRs, each labeled with a different lanthanide fluorophore canbe used, in the assays described herein. One TLR polypeptide can serveas a control. Alternatively, the method can be used to test compounds onmore than one TLR at a time, thus increasing the efficiency of screensfor molecules that interfere with TLR binding to its ligand. Thelanthanide fluorophore, europium (Eu) is excited at 340 nm and due to alarge Stokes shift, europium emits light at around 630 nm. In theseassays, if the ligand and receptor are in close proximity (e.g., boundto each other), fluorescence energy transfer between the donor(europium) and the acceptor (allophycocyanin (APC)) is observed andemission of APC can be detected.

In the present methods, TR-FRET can be used by labeling the TLR ofinterest with a donor label such as europium chelate, and a ligand ofthe TLR is labeled with an acceptor label such as allophycocyanin (APC).Test compounds are assayed in the method for their ability to disruptthe interaction between the TLR and its ligand as measured by a decreasein energy transfer between the donor and acceptor molecules.

Commercially available methods of performing TR-FRET are available andcan be adapted for use in the methods described herein, for example, theDELFIA® (PerkinElmer, Boston, Mass.) system for plate assays usingTR-fluorimetry probes can be used. Reagents and kits for labelingcompounds for use in such methods are available (e.g., LANCE™ andDELFIA™, PerkinElmer, Boston, Mass.). It should be noted that TR-FRETcan be used in any of the screening assays described herein.

Amplified Luminescent Proximity Homogenous Assay (ALPHA)

In some embodiments, the methods include the use of the AlphaScreen™Amplified Luminescent Proximity Homogeneous Assay (ALPHA) assays andreagents (PerkinElmer, Boston, Mass.), a bead-based assay system thatprovides very sensitive non-radioactive homogeneous assay technology forscreening of biological interactions and activities. The assay,illustrated in FIG. 6A, employs two kind of beads, a donor and anacceptor bead. Typically, the ligand is immobilized on one bead and thereceptor is immobilized on the other bead. The donor bead contains thephotosensitizer phthalocyanine which can covert oxygen to a singletoxygen after illumination of 680 nm light. The half-time of the lifetimeof singlet oxygen is around 4 μsec, during which the molecule diffusesaround 200 nm. If an acceptor bead is within a distance of less than 200nm to the donor bead, energy is transferred to a thioxene derivative inthe acceptor bead. This leads to the production of light in the range of520-620 nm.

TLR Interactors and Ligands

In general, any TLR ligand can be utilized in the assays describedherein. When TR fluorimetry methods are used, the ligand must be closeenough to the TLR polypeptide for the energy transfer between thelabeled TLR and TLR interactor to occur, e.g., bound directly to theTLR). Generally, known TLR ligands are used in the methods describedherein. Such molecules include ligands comprising a pathogen-associatedmolecular pattern (PAMP) derived from a pathogen, e.g., microorganisms(e.g., bacterial lipopolysaccharide, lipoproteins, peptidoglycans,bacterial or viral DNA or RNA) or parasites (e.g., GPI-anchors,schistosomal lysosphosphatidylserine). In some embodiments, theinvention includes the use of other TLR activating agents such assynthetic compounds (e.g., DNA, RNA, synthetic lipopeptides) orTLR-interacting drugs (e.g., amphotericin, resiquimod, imiquimod) andendogenous TLR interacting molecules (e.g., heat-shock proteins).

TLRs and Cell Lines

Toll-like receptors (TLRs) are a family of type I integral membraneglycoproteins. All of the family members are characterized by thepresence of two regions of leucine rich repeats (LRR)-containing in theN-terminal (“extracellular”) domain and a toll interleukin 1 resistance(TIR) domain in the intracellular portion (see, e.g., Bell et al., 2003,Trends Immunol., 24(10):528-33).

At least ten different TLRs have been identified (Takeda et al., 2003,Ann. Rev. Immunol., 21:335-376. Epub 2001 December 19; Barton andMedzhitov, 2002, Curr. Top. Microbiol. Immunol., 270:81-92). Any TLRpolypeptide can be used in the assays described herein, provided that amethod of producing the TLR polypeptide is available. In general, TLRnucleic acid sequences are known, and can be cloned and expressed usingmethods known in the art. Suitable toll-like receptors include, but arenot limited to, toll-like receptor 1, Homo sapiens (GeneID: 7096;UniGene Cluster Hs.111805; NCBI Accession #NP_(—)003254.2, AAC34137.1);toll-like receptor 2, Homo sapiens (GeneID: 7097; UniGene ClusterHs.519033; NCBI Accession #AAH33756.1, AAM23001.1, AAC34133.1);toll-like receptor 3, Homo sapiens (GeneID: 7098; UniGene ClusterHs.29499; NCBI Accession #AAC34134.1, NP_(—)003256.1); toll-likereceptor 4, Homo sapiens (GeneID: 7099 (var. C); UniGene ClusterHs.174312; NCBI Accession #AAC34135.1, AAF89753.1, AAF07823.1,AAF05316.1); toll-like receptor 5, Homo sapiens (GeneID: 7100; UniGeneCluster Hs.114408; NCBI Accession #AAC34136.1, BAB43955.1); toll-likereceptor 6, Homo sapiens (GeneID: 10333; UniGene Cluster Hs.366986; NCBIAccession #NP_(—)006059.2, BAA78631.1); toll-like receptor 7, Homosapiens (GeneID: 51284; UniGene Cluster Hs.179152; NCBI Accession#AAF60188.1, AAF78035.1, NP_(—)057646.1, AAH33651.1); toll-like receptor8, Homo sapiens (GeneID: 51311; UniGene Cluster Hs.272410; NCBIAccession #AAF64061.1, AAF78036.1); toll-like receptor 9 Homo sapiens(GeneID: 54106; UniGene Cluster Hs.87968; NCBI Accession # AAG01734.1,AAG01735.1, AAG01736.1, BAB19259.1); toll-like receptor 10, Homo sapiens(GeneID: 81793; UniGene Cluster Hs.120551; NCBI Accession #AAK26744.1,NP_(—)112218.1); toll-like receptor 1, Mus musculus (GeneID: 21897;UniGene Cluster Mm.273024; NCBI Accession #AAG35062.1, AAG37302.1,NP_(—)109607.1); toll-like receptor 2, Mus musculus (GeneID: 24088;UniGene Cluster Mm.87596; NCBI Accession #AAD46481.1, AAF04277.1,AAD49335.1, NP_(—)036035.2, AAF28345.1); toll-like receptor 3, Musmusculus (GeneID: 142980; UniGene Cluster Mm.33874; NCBI Accession#AAK26117.1, AAL27007.1, NP_(—)569054.2); toll-like receptor 4, Musmusculus (GeneID: 21898; UniGene Cluster Mm.38049; NCBI Accession#AAD29272.1, AAF04278.1, AAF05317.1, NP_(—)067272.1, AAH29856.1);toll-like receptor 5, Mus musculus (GeneID: 53791; UniGene ClusterMm.116894, Mm.347908; NCBI Accession #AAF65625.1, NP_(—)058624.1);toll-like receptor 6, Mus musculus (GeneID: 21899; UniGene ClusterMm.42146, Mm.347552; NCBI Accession #BAA78632.1, AAG38563.1,NP_(—)035734.1); toll-like receptor 7, Mus musculus (GeneID: 170743;UniGene Cluster Mm.23979; NCBI Accession #AAK62676.1, NP_(—)573474.1,AAL73191.1, AAL73192.1); toll-like receptor 8, Mus musculus (GeneID:170744; UniGene Cluster Mm.196676; NCBI Accession #NP_(—)573475.1,AAK62677.1); and toll-like receptor 9, Mus musculus (GeneID: 81897;UniGene Cluster Mm.44889; NCBI Accession #BAB19260.1, AAK29625.1,AAK28488.1, NP_(—)112455.1); and homologs thereof. In some embodiments,the TLR is TLR2 or TLR9.

In addition, methods of engineering a TLR fusion protein (e.g., with afluorescent protein) suitable for use in the assays are within the scopeof the art (e.g., Latz et al., 2002, supra). As described herein,TLR-fluorescent protein fusion proteins can be engineered to enabletracking the TLR by virtue of the molecular tag in a variety ofexperimental systems. TLR-Fc fusion proteins can also be used, see U.S.Provisional Patent Application Ser. No. 60/598,774, filed Aug. 4, 2004,the disclosure of which is incorporated by reference herein. Stable celllines have been established using such methods (e.g., Latz et al., 2002,supra). The stable cell lines have the common characteristic of stablyexpressing a chimeric fluorescent TLR. In general, the chimericfluorescent TLR can, upon stimulation of the cell by a molecule known toactivate the signaling pathway of the naturally occurring cognate of thechimeric TLR, induce one or more activities of the signaling pathway.

In some cases, TLRs recognize their cognate ligands by formingoligomeric complexes with other members of the family. This appears tobe the case for TLR2, which requires cooperation with TLR1 or TLR6 inorder to recognize certain ligands, e.g., Pam3CysK4 or Pam2CysK4,respectively. In such cases, both TLRs that are present in theheteromeric complex are used in the assay. For example, both TLRs thatare naturally found in a heterodimer are coated onto an assay plate orare used in solution. If both are to be coated onto a prepared plate(e.g., a plate pre-coated with an antibody), then both TLRs are labeledwith an attachment moiety (tag), e.g., hemagglutinin, biotion, GFP. Inassays in which more than one TLR is being used and the TLRs are presentin a liquid phase (e.g., for presentation in a plate assay in which theplate contains immobilized TLR ligand), the TLRs are provided insolution in approximately equal amounts or equal amounts of cell lysatesfrom cells that express each TLR are used. One or both TLRs can belabeled (e.g., expressed as fusion proteins with a fluorescent protein)for subsequent detection steps.

Compounds

The test compounds used in screening assays can be obtained from anysources known in the art including any of the numerous approaches incombinatorial library methods known in the art such as biologicallibraries; peptoid libraries (libraries of molecules having thefunctionalities of peptides, but with a novel, non-peptide backbonewhich are resistant to enzymatic degradation but which neverthelessremain bioactive (e.g., Zuckermann et al., 1994, J. Med. Chem.37:2678-85); spatially addressable parallel solid phase or solutionphase libraries; synthetic library methods requiring deconvolution; the‘one-bead one-compound’ library method; and synthetic library methodsusing affinity chromatography selection. The biological library andpeptoid library approaches are limited to peptide libraries, while theother four approaches are applicable to peptide, non-peptide oligomer orsmall molecule libraries of compounds (Lam, 1997, Anticancer Drug Des.12:145).

Examples of methods for the synthesis of molecular libraries can befound in the art, for example in: DeWitt et al. (1993, Proc. Natl. Acad.Sci. U.S.A. 90:6909), Erb et al. (1994, Proc. Natl. Acad. Sci. USA91:11422), Zuckermann et al. (1994, J. Med. Chem. 37:2678), Cho et al.(1993, Science 261:1303), Carrell et al. (1994, Angew. Chem. Int. Ed.Engl. 33:2059), Carell et al. (1994, Angew. Chem. Int. Ed. Engl.33:2061), and in Gallop et al. (1994, J. Med. Chem. 37:1233).

Libraries of compounds (or individual compounds or pools of compounds)can be presented as is appropriate for a particular assay. In general,compounds are presented in solution (e.g., Houghten, 1992, Biotechniques13:412-421), or on beads (Lam, 1991, Nature 354:82-84). Libraries canalso be presented on chips (Fodor, 1993, Nature 364:555-556), bacteria(Ladner, U.S. Pat. No. 5,223,409), spores (Ladner, U.S. Pat. No.5,223,409), plasmids (Cull et al., 1992, Proc. Natl. Acad. Sci. USA89:1865-1869) or on phage (Scott and Smith, 1990, Science 249:386-390;Devlin, 1990, Science 249:404-406; Cwirla et al., 1990, Proc. Natl.Acad. Sci. USA 87:6378-6382; Felici, 1991, J. Mol. Biol. 222:301-310;Ladner, supra).

Biotinylation

In some cases molecules are biotinylated for use in the assays describedherein. Methods known in the art can be used. For example, ligands thatcontain primary amine-groups can be biotinylated in a one-step procedureusing commercially available reagents. Lipopolysaccharides can belabeled with biotin in a two-step procedure as described in the art(e.g., Visintin et al., 2003, J. Biol. Chem. Online reference10.1074/jbc.M306802200, September. 5). Synthetic compounds can besynthesized with biotin (e.g., biotinylated CpG-DNA or biotinylatedPam3CysK4).

Correlating Information

The invention also relates to methods for correlating information abouta test compound. Correlating means showing a relationship between a testcompound and modulation of the interaction between a TLR polypeptide anda TLR ligand, to identify the compound as a compound that can modulateimmune system activity. The correlating step can include, e.g.,generating or providing a record, e.g., a printed computer-readablerecord, such as a laboratory record, electronic mail, or dataset,including information regarding a plurality of test compounds and theirability to modulate an interaction (e.g., binding) between a TLRpolypeptide and a TLR ligand. The record can also include informationabout whether the test compound can, e.g., modulate TLR activity, and/ormodulate immune system activity. The record can include otherinformation, such as a specific test compound identifier, a date, anoperator of the method, and/or information about the source, structure,method of purification or biological activity of the test compound. Therecord or information derived from the record can be used, e.g., toidentify the test compound as a compound or candidate compound (e.g., alead compound) for pharmaceutical or therapeutic use. The identifiedcompound can be identified as an agent or a potential agent fortreatment of diabetic nephropathy. Agents, e.g., compounds, identifiedby this method can be used, e.g., in the treatment (or development oftreatments) for immune system related disorders or for increasing theactivity of the immune system (e.g., as adjuvants for vaccineadministration).

Uses

The methods and reagents described herein can be used in automatedscreening of large compound libraries to identify compounds that caninteract with a TLR (e.g., TLR9). Compounds that bind to the TLRgenerally have the ability to either displace binding of a TLRinteractor (e.g., ligand such as CpG-DNA) when the TLR interactor isbound to the TLR. In other embodiments, the compound, when immobilized(e.g., in a microtiter well) will directly bind the TLR. Once a compoundis identified that can interact with the selected TLR, the compound canbe characterized for function (e.g., agonistic, antagonistic,competitive, or cooperative activity). The compounds can be furthertested for their ability to modulate TLR signaling, for example, byassaying the ability of the compound to modulate one or more indicia ofactivation of TLR signaling by the selected TLR. For example, expressionof an RNA or protein, or an enzymatic activity known to be induced aspart of the signaling of the selected TLR, (e.g., activation of NF-κB).Compounds can also be tested for their suitability for treating asubject in need of treatment.

The solid phase assay can be used to characterize the thermodynamicconstants of the interaction of TLRs and their ligands. For example aTLR and a nucleic acid or nucleic acid analog. This information isuseful for assessing the pharmacokinetic potential of the compound.

Compounds that stimulate or enhance TLR signaling are useful, forexample, as immunostimulants. Immunostimulants can be useful fortreating subjects who are immunocompromised or as adjuvants forincreasing the response to a vaccine. Compounds that inhibit TLRsignaling are useful, for example, as inhibitors of undesirableinflammatory responses or to inhibit an undesirable immune response asin certain inflammatory diseases such as rheumatoid arthritis orsystemic lupus erythematosus.

Pharmaceutical Compositions and Methods of Administration

The therapeutic compounds described herein can be incorporated intopharmaceutical compositions. Such compositions typically include thenucleic acid molecule and a pharmaceutically acceptable carrier. As usedherein the language “pharmaceutically acceptable carrier” includessaline, solvents, dispersion media, coatings, antibacterial andantifungal agents, isotonic and absorption delaying agents, and thelike, compatible with pharmaceutical administration. Supplementaryactive compounds can also be incorporated into the compositions.

Pharmaceutical compositions are typically formulated to be compatiblewith its intended route of administration. Examples of routes ofadministration include parenteral, e.g., intravenous, intradermal,subcutaneous, oral (e.g., inhalation), transdermal (topical),transmucosal, and rectal administration. Solutions or suspensions usedfor parenteral, intradermal, or subcutaneous application can include thefollowing components: a sterile diluent such as water for injection,saline solution, fixed oils, polyethylene glycols, glycerine, propyleneglycol or other synthetic solvents; antibacterial agents such as benzylalcohol or methyl parabens; antioxidants such as ascorbic acid or sodiumbisulfite; chelating agents such as ethylenediaminetetraacetic acid;buffers such as acetates, citrates or phosphates and agents for theadjustment of tonicity such as sodium chloride or dextrose. pH can beadjusted with acids or bases, such as hydrochloric acid or sodiumhydroxide. The parenteral preparation can be enclosed in ampoules,disposable syringes or multiple dose vials made of glass or plastic.

Pharmaceutical compositions suitable for injectable use can includesterile aqueous solutions (where water soluble) or dispersions andsterile powders for the extemporaneous preparation of sterile injectablesolutions or dispersion. For intravenous administration, suitablecarriers include physiological saline, bacteriostatic water, CremophorEL™ (BASF, Parsippany, N.J.) or phosphate buffered saline (PBS). In allcases, the composition must be sterile and should be fluid to the extentthat easy syringability exists. It should be stable under the conditionsof manufacture and storage and must be preserved against thecontaminating action of microorganisms such as bacteria and fungi. Thecarrier can be a solvent or dispersion medium containing, for example,water, ethanol, polyol (for example, glycerol, propylene glycol, andliquid polyethylene glycol, and the like), and suitable mixturesthereof. The proper fluidity can be maintained, for example, by the useof a coating such as lecithin, by the maintenance of the requiredparticle size in the case of dispersion and by the use of surfactants.Prevention of the action of microorganisms can be achieved by variousantibacterial and antifungal agents, for example, parabens,chlorobutanol, phenol, ascorbic acid, thimerosal, and the like. In manycases, it will be preferable to include isotonic agents, for example,sugars, polyalcohols such as mannitol, sorbitol, sodium chloride in thecomposition. Prolonged absorption of the injectable compositions can bebrought about by including in the composition an agent which delaysabsorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions can be prepared by incorporating the activecompound in the required amount in an appropriate solvent with one or acombination of ingredients enumerated above, as required, followed byfiltered sterilization. Generally, dispersions are prepared byincorporating the active compound into a sterile vehicle, which containsa basic dispersion medium and the required other ingredients from thoseenumerated above. In the case of sterile powders for the preparation ofsterile injectable solutions, the preferred methods of preparation arevacuum drying and freeze-drying which yields a powder of the activeingredient plus any additional desired ingredient from a previouslysterile-filtered solution thereof.

Oral compositions generally include an inert diluent or an ediblecarrier. For the purpose of oral therapeutic administration, the activecompound can be incorporated with excipients and used in the form oftablets, troches, or capsules, e.g., gelatin capsules. Oral compositionscan also be prepared using a fluid carrier for use as a mouthwash.Pharmaceutically compatible binding agents, and/or adjuvant materialscan be included as part of the composition. The tablets, pills,capsules, troches and the like can contain any of the followingingredients, or compounds of a similar nature: a binder such asmicrocrystalline cellulose, gum tragacanth or gelatin; an excipient suchas starch or lactose, a disintegrating agent such as alginic acid,Primogel, or corn starch; a lubricant such as magnesium stearate orSterotes; a glidant such as colloidal silicon dioxide; a sweeteningagent such as sucrose or saccharin; or a flavoring agent such aspeppermint, methyl salicylate, or orange flavoring.

For administration by inhalation, the compounds are delivered in theform of an aerosol spray from pressured container or dispenser whichcontains a suitable propellant, e.g., a gas such as carbon dioxide, or anebulizer. Such methods include those described in U.S. Pat. No.6,468,798.

Systemic administration of a therapeutic compound as described hereincan also be by transmucosal or transdermal means. For transmucosal ortransdermal administration, penetrants appropriate to the barrier to bepermeated are used in the formulation. Such penetrants are generallyknown in the art, and include, for example, for transmucosaladministration, detergents, bile salts, and fusidic acid derivatives.Transmucosal administration can be accomplished through the use of nasalsprays or suppositories. For transdermal administration, the activecompounds are formulated into ointments, salves, gels, or creams asgenerally known in the art.

The therapeutic compounds can also be prepared in the form ofsuppositories (e.g., with conventional suppository bases such as cocoabutter and other glycerides) or retention enemas for rectal delivery.

Therapeutic compounds comprising nucleic acids can be administered byany method suitable for administration of nucleic acid agents, such as aDNA vaccine. These methods include gene guns, bio injectors, and skinpatches as well as needle-free methods such as the micro-particle DNAvaccine technology disclosed in U.S. Pat. No. 6,194,389, and themammalian transdermal needle-free vaccination with powder-form vaccineas disclosed in U.S. Pat. No. 6,168,587. Additionally, intranasaldelivery is possible, as described in, inter alia, Hamajima et al.,Clin. Immunol. Immunopathol., 88(2), 205-10 (1998). Liposomes (e.g., asdescribed in U.S. Pat. No. 6,472,375) and microencapsulation can also beused. Biodegradable targetable microparticle delivery systems can alsobe used (e.g., as described in U.S. Pat. No. 6,471,996).

In one embodiment, the therapeutic compounds are prepared with carriersthat will protect the therapeutic compounds against rapid eliminationfrom the body, such as a controlled release formulation, includingimplants and microencapsulated delivery systems. Biodegradable,biocompatible polymers can be used, such as ethylene vinyl acetate,polyanhydrides, polyglycolic acid, collagen, polyorthoesters, andpolylactic acid. Such formulations can be prepared using standardtechniques. The materials can also be obtained commercially from AlzaCorporation and Nova Pharmaceuticals, Inc. Liposomal suspensions(including liposomes targeted to infected cells with monoclonalantibodies to viral antigens) can also be used as pharmaceuticallyacceptable carriers. These can be prepared according to methods known tothose skilled in the art, for example, as described in U.S. Pat. No.4,522,811.

Dosage, toxicity and therapeutic efficacy of the therapeutic compoundscan be determined by standard pharmaceutical procedures in cell culturesor experimental animals, e.g., for determining the LD50 (the dose lethalto 50% of the population) and the ED50 (the dose therapeuticallyeffective in 50% of the population). The dose ratio between toxic andtherapeutic effects is the therapeutic index and it can be expressed asthe ratio LD50/ED50. Compounds which exhibit high therapeutic indicesare preferred. While compounds that exhibit toxic side effects may beused, care should be taken to design a delivery system that targets suchcompounds to the site of affected tissue in order to minimize potentialdamage to uninfected cells and, thereby, reduce side effects.

The data obtained from the cell culture assays and animal studies can beused in formulating a range of dosage for use in humans. The dosage ofsuch compounds lies preferably within a range of circulatingconcentrations that include the ED50 with little or no toxicity. Thedosage may vary within this range depending upon the dosage formemployed and the route of administration utilized. For any compound usedin the method of the invention, the therapeutically effective dose canbe estimated initially from cell culture assays. A dose may beformulated in animal models to achieve a circulating plasmaconcentration range that includes the IC50 (i.e., the concentration ofthe test compound which achieves a half-maximal inhibition of symptoms)as determined in cell culture. Such information can be used to moreaccurately determine useful doses in humans. Levels in plasma may bemeasured, for example, by high performance liquid chromatography.

A therapeutically effective amount of a therapeutic compound (i.e., aneffective dosage) depends on the therapeutic compounds selected. Thecompositions can be administered one from one or more times per day toone or more times per week; including once every other day. The skilledartisan will appreciate that certain factors may influence the dosageand timing required to effectively treat a subject, including but notlimited to the severity of the disease or disorder, previous treatments,the general health and/or age of the subject, and other diseasespresent. Moreover, treatment of a subject with a therapeuticallyeffective amount of the therapeutic compounds described herein caninclude a single treatment or a series of treatments.

The pharmaceutical compositions can be included in a container, pack, ordispenser together with instructions for administration.

EXAMPLES

The following examples illustrate certain embodiments of the methods butare not to be construed as limiting.

Materials

Reagents. Monoclonal antibody and polyclonal antiserum against GFP wereobtained from Clontech (Palo Alto, Calif.) and Molecular Probes (Eugene,Oreg.), respectively. The HRP-conjugated polyclonal anti-biotin antibodywas from New England Biolabs (Beverly, Mass.). Unless otherwise stated,other reagents were purchased from Sigma. Phosphothioate CpG-DNA wasfrom MWG Biotech (High Point, N.C.). DNA was labeled at the 3-prime endwith either fluorescent tags or biotin. The sequences of stimulatoryCpG-DNA were as described in Bauer et al. (2001, Proc. Natl. Acad. Sci.USA 98: 9237-9242). R848 is a commercially available (e.g., InvivoGen,San Diego, Calif.) and is an imidazoquinoline compound that stimulatesactivation of immune cells via TLR7/TLR8 pathways. CpG1668 is asdescribed in Sparwasser et al. (1997, Nature 386:336-337).

Cellular Activation Assays—Dual Luciferase Reporter Assays for NF-κBActivation

Cellular activation was assessed by NF-κB-luciferase reporter assay.Briefly, HEK293 cells that stably express a TLR^(FP) or empty vector(pcDNA) were seeded into 96-well tissue culture plates at a density of2×10⁴ cells/well. The following day, cells were transiently transfectedwith luciferase reporter genes using Genejuice (Novagen) per themanufacturer's recommendations. In order to assess NF-κB activation, anNF-κB-luciferase reporter gene consisting of an artificial promotercomposed of a multimer of five NF-κB sites driving the fireflyluciferase gene, was co-transfected with a constitutively activeRenilla-luciferase reporter gene (Promega, Madison, Wis.).

Ligand-binding studies. Monolayers of cells expressing chimeric TLRswere incubated for 8 hours with 5 μM biotinylated CpG-DNA before lysis(Latz et al., 2002, supra) and microcentrifugation to remove nucleardebris. Alternatively, clarified cellular lysates were incubated with 5μM biotinylated CpG-DNA. Streptavidin-coated beads (Sigma) (25 μl of a50% suspension) were added to 500 μl of lysate and rotated for one hourat 4° C. In a parallel experiment, lysates were incubated with anti-GFPpolyclonal antibody and 40 μl of packed protein A-Sepharose™ at 4° C.for one hour to assess overall protein levels of the chimeric TLRs.Pellets were washed four times in lysis buffer, resolved by SDS-PAGE,and transferred to nitrocellulose membranes (HyBond C, AmershamBiosciences). Membranes were blocked in 5% powdered milk (Gibco) andblotted with anti-GFP monoclonal antibody. Blots were then incubatedwith HRP-conjugated anti-mouse antibody and developed on Hyperfilm™ withthe enhanced chemiluminescence HRP substrate system (AmershamBiosciences).

Example 1 TLR Plate Assay

Plate or solid phase assays are useful for identifying compounds thatcan modulate the interaction between a TLR and a TLR ligand. Todemonstrate the principle of such plate assays, microtiter plates werecoated with 0.3 μM biotinylated CpG-DNA (phosphothioate-stabilized CpGoligodeoxynucleotides, 2006; TCGTCGTTTTGTCGTTTTGTCGTT (SEQ ID NO:1) inPBS, and washed with PBS/0.05% Tween 20. Plates were generally freshlyprepared but optionally can be stored before use. Control wells in theplates were only processed as for coating using phosphate bufferedsaline (PBS).

Fluorescent DNA constructs. TLR2^(YFP) and TLR4^(YFP) constructs were asdescribed in Latz et al. (2002, J. Biol. Chem. 277:47834-47843). PCR ofTLR9 was performed to construct chimeric fluorescent cDNAs. The primersfor TLR9 were: 5′-GAAGCCCCTGCCCGGATCCATGGGTTTCTGC-3′ (SEQ ID NO:2) and5′-TCCGGCTCACTCGAGTTCGGCCGTGGGTCCCTG-3′ (SEQ ID NO:3). PCR fragmentswere cloned into the BamHI and XhoI sites of pcDNA3-CFP, pcDNA3-YFP andpcDNA3-GFP (Latz et al., 2002, supra). Retroviral constructs containingTLR9^(YFP) and MyD88^(CFP) were constructed similarly; PCR products werecloned into peak12 mmp.

For the assay, the plates were incubated with cellular lysates (preparedas described above) from TLR9^(YFP) or TLR4^(YFP) (as a control forspecificity) expressing HEK cells for one hour at room temperature. Theplates were then washed and incubated with 0.5 μg/ml of a monoclonalanti-GFP antibody (Molecular Probes, Inc.) for one hour at roomtemperature. The plates were washed three times with PBS/Tween 20 0.05%at room temperature and the bound antibody was detected by incubatingwith an anti-mouse IgG conjugated to horseradish peroxidase (HRP) forone hour at room temperature. The plates were developed by addingHRP-substrate and the color development was quantified by absorbancemeasurements at 450 nm after stopping the reaction by addition of 2 NNaHCO₃ to bring the concentration to 2N in a final volume of 200 μl.

The results of these experiments demonstrate the specificity of theassay since only TLR9^(YFP) binding to CpG-DNA was detected at a levelabove control and significant binding of TLR4^(YFP) was not observed(FIG. 3A). Such assays can be modified for testing the ability of acompound to modulate the interaction between the TLR and aTLR-interactor (e.g., ligand). In addition, the ability of a moleculesuspected of being able to interact with a TLR can be tested. Forexample, the compound can be biotinylated using methods known in the artand binding the biotinylated molecule to the plate instead of, e.g.,biotinylated CpG-DNA.

In another design of the plate assay, anti-GFP coated microtiter plates(Pierce) were used to immobilize the TLR-fluorescent protein fusionprotein and were used directly after coating with the TLR. The plateswere incubated with cell lysates prepared from cells that stably expressTLR9^(YFP) or TLR4^(YFP) for one hour at room temperature, washed threetimes with PBS/Tween 20 (0.05%), and then incubated with biotinylatedCpG-DNA (2006); 0.01 μM) for one hour at room temperature, and washedagain three times with PBS/Tween 20 (0.05%). Bound ligand was detectedby incubating the plates with HRP-conjugated streptavidin for one hourat room temperature, washing with PBS/Tween 20 (0.05%), and detectingusing HRP substrate (R and D) and determining the absorbance at 450 nm.The results of these experiments were similar to those in which theCpG-DNA was the immobilized component of the assay in that significantbinding was observed only when the two interactants were CpG-DNA andTLR9^(YFP) (FIG. 3B).

This assay can be adapted for use in drug-screening applications. Forexample, the interaction of TLR9 with CpG-DNA reflects a clinicallyimportant receptor/ligand interaction since a variety of autoimmunediseases are thought to be based on the interaction of DNA-antibodycomplexes with this receptor (Leadbetter et al., 2002, Nature416:603-607). Thus, antagonists for this interaction are useful for thedevelopment of novel anti-inflammatory drugs. To examine the applicationof this assay to the identification of such compounds (e.g., compoundsthat increase or decrease the interaction) and so are potential drugsfor ameliorating TLR-related disorders, a competition assay wasdeveloped that was based on the basic plate assay described above. Thecompetition assay was performed essentially as described above for theplate assay. In addition, non-biotinylated CpG-DNA (“cold ligand”) orother compounds that interfere with TLR9 signaling (R848 or bacterialDNA) were added to the TLR9-containing lysates. The ability of thevarious compounds to inhibit binding of TLR9^(YFP) to the plate-boundbiotinylated CpG-DNA was then evaluated. Since the ability of variouscompounds to inhibit binding was observed, these data demonstrate thatthe assay can be used to identify compounds that modulate theinteraction of a TLR with a TLR interactor.

Example 2 Binding of CpG-DNA to TLR-9 is Saturable

Experiments were performed to determine the affinity of TLR9 to CpG-DNA(2006). In these experiments cellular lysates were prepared fromHEK-TLR9^(YFP) cells. NeutrAvidin™ microtiter plates (Pierce) werecoated with various concentrations of CpG-DNA (2006) and incubated withthe cellular lysates. After washing, the plates were incubated withanti-GFP monoclonal GFP, washed, incubated with anti-mouse-HRP, thendetected with a color reaction to detect HRP activity. Absorbance wasmeasured at 450 nm. The results of the experiments are shown in FIG. 4.

Binding of TLR9 to CpG-DNA was saturated at approximately 0.3 μM CpG-DNAand half-maximal binding was observed at 0.02 μM. Thus, the Kd of humanTLR9 for CpG-DNA (2006-sequence) is around 20 nM (FIG. 4).

These data demonstrate that the characteristics of binding of a TLR to aTLR-interactor can be assayed using the plate assay. Such assays canalso be used to evaluate the effects of a compound on the interactionbetween TLR and a TLR-interactor by either incubating a compound in theligand-coated plate before adding the TLR or adding the compound withthe TLR then assaying the amount of TLR associated with the ligand asdescribed above and comparing the amount of association in the presenceand absence of the compound. A decrease in the amount the associationbetween TLR and the TLR-interactor in the presence of the compoundindicates that the compound can decrease the interaction. A furthervariation on the assay is addition of the compound to the coated plateafter the plate has been incubated with the TLR. Various concentrationsof the compound are used or the compound can be added for various times.The assay is then carried out as described above. The resultsdemonstrate the ability of the compound to displace the TLR in itsinteraction with the TLR interactor (e.g., ligand).

Example 3 Non-labeled CpG-DNA Competes for TLR9-CpG-DNA Interaction

One useful application of the TLR ligand binding assay is its use indrug-screening applications. For example, the interaction of TLR9 withCpG-DNA reflects a clinically important receptor/ligand interactionsince a variety of auto-immune diseases are thought to be based on theinteraction of DNA-antibody complexes with TLR9. Thus, antagonists forthis interaction would obviously have a role in the development of novelanti-inflammatory drugs. To examine whether this assay is useful as adrug-screening assay, a competition assay was devised.

In the assay, NeutrAvidin™ plates (Pierce) were coated with 0.3 μMbiotin-CpG-DNA 2006 as described above. Non-biotinylated CpG-DNA (“coldligand”; CpG-DNA 2006 or CpG-DNA 1668, the mouse TLR9 optimalstimulating sequence) or other compounds that interfere with TLR9signaling (R848 and bacterial DNA) were added to TLR9^(YFP)-containingcell lysates. These lysates were then added to the plate boundbiotinylated CpG-DNA and processed as described above to detect theamount of binding of TLR9^(YFP) bound to the plates.

The drug R848 inhibited TLR9 signaling in a dose dependent manner inTLR9-expressing HEK cells but did not interfere with the binding of TLR9to CpG-DNA (FIGS. 5A-D). Genomic bacterial DNA in its unprocessed formdid not induce TLR9 signaling in these experiments. Finally, when twodifferent CpG-oligonucleotides were incubated with increasingconcentrations of non-biotinylated CpG-DNA (2006 or 1668 sequence), dosedependent inhibition of TLR9 binding to biotinylated immobilized CpG-DNAwas observed.

These data demonstrate that assays such as those described herein (e.g.,a plate assay) can be used to test the ability of a compound to modulatethe interaction between a TLR and TLR-interactor (e.g., a TLR ligand).

Example 4 Purification of TLR Fusion Proteins

In some cases, the use of a purified TLR, e.g., TLR-fluorescent fusionprotein (TLR^(FFP)), is used. Purified proteins can improve thesensitivity of the assay system. For example, after preparing a celllysate from a cell line that stably expresses a TLR9^(GFP,) the fusionprotein is purified by affinity chromatography. In a typicalpurification protocol, an anti-GFP antibody is immobilized on a solidmatrix using common established protocols (column resins such asactivated agarose beads, are commercially available from severalcompanies such as Pierce and Amersham). The TLR9^(GFP) containingcellular lysate is then mixed with the antibody containing beads for onehour at 4° C. Beads are then extensively washed in lysis buffer andpurified TLR9 eluted in low pH (glycine buffer pH 2.2).

Example 5 Amplified Luminescent Proximity Homogenous Assay (ALPHA)

To demonstrate the use of the Perkin Elmer AlphaScreen™ assay technology(illustrated in FIG. 6A) for the probing of receptor/ligand interactionof TLRs, the assay was performed with a purified TLR9-Fc fusion proteinand biotinylated DNA. 10 μg/ml purified TLR9-Fc protein was incubatedwith increasing doses of biotinylated CpG-DNA for 1 hour in the wells ofa 385 well plate. Thereafter, streptavidin-coated donor beads andprotein A-coated acceptor beads were added and the mixture was incubatedfor another hour at room temperature. The buffer system used for thisassay was as follows: MES 50 mM, NaCl 150 mM, CaCl₂ 1 mM, 0.1% BSA,0.01% Tween™ 20, pH6.

FIG. 6B shows a representative experiment of CpG-DNA/TLR9-Fcinteraction. Two kinds of DNA were interacted with TLR9-FC in thisexperiment. The 2006 sequence (described above) and the 2006GC sequence.The ligand was titrated over a range of 0.01 nM to 1000 nM. Thebell-shaped curves that were obtained represent both binding of DNA toTLR9-FC up to saturation of the beads (maximal AlphaScreen units) andblocking of the assay signal by excess ligand (downward slope of thecurve after saturation). By adding excess ligand (more than the bindingcapacity of the streptavidin coated beads) one is able to obtain bindingand blocking of the signal in the same experiment.

Example 6 TLR2 is Activated by PorinB in Living Cells

TLR2 binds and is triggered by a variety of bacterial derived molecularsignatures, such as lipoproteins (proteins anchored to the bacterialwall via lipid anchors), outer membrane proteins (proteins involved inbacteria metabolism, such as ion channels) and peptidoglycan (the“fabric” of all bacteria's cell wall) (Beutler et al., 2003, J. Leukoc.Biol., 74(4):479-85).

Because of its wide range of ligands, TLR2 is an optimal candidate forscreening for TLR interactors that are biologic response modifiers(Beutler, 2004, Nature, 430(6996):257-63), e.g., activators (e.g.,vaccine adjuvants (Schjetne et al., 2003, J. Immunol., 171(1):32-6) andblockers (e.g., anti-inflammatory compounds (Meng et al., 2004, J. Clin.Invest., 113(10):1473-81)). In the following examples, we report avariety of binding assays involving the interaction of TLR2 with theprotein PorinB from Neisseria meningitidis and a synthetic prototypiclipopeptide, Pam2CysK4.

293 cells stably expressing TLR4/MD-2 (as described in Visintin et al.,2003, J. Biol. Chem., 278(48):48313-48320) or TLR2 were stimulated usinglipopolysaccharide (LPS) or PorinB, and the extent of activationmeasured as the activation of a NF-κB-dependent reporter gene encodingfor the Luciferase gene. To measure NF-κB activation, 2 μg of a reporterplasmid in which NF-κB drives the synthesis of luciferase wastransiently cotransfected with 5 μg of the indicated cDNA by lipofection(GeneJuice) in 10-cm tissue culture dishes following the manufacturer'srecommendations. The following morning, cells were seeded at a densityof 50,000 cells/well in a 96-well plate, allowed to recover for 5 hours,and stimulated as indicated between 6 and 18 hours. Luciferase activitywas measured with a plate reader luminometer (Victor², PerkinElmer LifeSciences) using chemicals provided with the luciferase assay system(Promega, Madison, Wis.). All data are presented as the means±S.D. oftriplicate well readings, normalized to a value of 1.0 in comparisonwith an unstimulated negative control.

The results are shown in FIGS. 7A-B. The different gray tones correspondto the concentrations of stimulant used. LPS, a well known TLR4/MD-2agonist, could activate TLR4/MD-2 (7A) expressing reporter cells, butfailed to activate TLR2 expressing cells (7B). On the contrary, PorinBefficiently activates TLR2 expressing cells, but not TLR4/MD-2 reportercells. This data demonstrates that PorinB is likely to interact withTLR2, and that this method can be used to assay receptor activationafter stimulation with a ligand.

Example 7 TLR2 Binds to PorinB in Living Cells

In order to develop a binding assay for TLR2 and PorinB, the TLR proteinwas biotinylated using standard chemistry (Pierce Biotechnology, Inc.,Rockford, Ill.). Briefly, adherent cells from a confluent 10-cm dishwere labeled with biotin (Pierce) on ice, solubilized in detergent (1%Triton X-100, 10 mM Tris-Cl (pH 7.4), 137 mM NaCl, 10% glycerol, 2 mMEDTA, and protease inhibitors), subjected to immunoprecipitation withthe appropriate antibodies (2 μg/ml) in 20 μl of packed proteinA-Sepharose (Amersham Biosciences, Uppsala, Sweden) for 16 hours at 4°C., resolved by SDS-PAGE, and electro-transferred onto Hybond-C™nitrocellulose membranes (Amersham Biosciences). The membranes wereblocked in 5% dry milk in phosphate-buffered saline (PBS) and 0.1% Tween20 for 30 minutes at 37° C. and probed for an additional 30 minutes at37° C. with horseradish peroxidase-conjugated anti-biotin polyclonalantibody (1 μg/ml). Biotinylated proteins were revealed by enhancedchemiluminescence using a commercial kit for this purpose (AmershamBiosciences). When necessary, membranes were stripped for 30 min in 0.1M glycine (pH 2.2), 1% Tween 20, and 0.1% SDS and reprobed.

In FIG. 7C, an anti biotin western immunoblotting performed onbiotinylated Porin is shown to demonstrate essential purity of thepreparation. The binding of Porin to living cells was then assessed, asshown in FIG. 7D. Adherent cells expressing a GFP-tagged TLR2 moleculewere incubated with 10 mg/ml of biotinylated PorinB for different timeperiods and then extensively washed. Cells were solubilized in lysisbuffer (10 mM Tris, pH 7.4, 137 mM NaCl, 0.5% Triton X-100, 2 mM EDTA,10% glycerol, and protease inhibitors) and biotin was captured withstreptavidin beads. The pellets were then separated by electrophoresisand western blotted using an anti GFP monoclonal antibody to reveal TLR2(enhanced chemiluminescence, Amersham-Pharmacia).

These results demonstrate that this method can be used for the screeningof molecules that can interfere with the binding of a ligand, e.g.,biotinylated PorinB to living cells expressing a tagged version of aTLR, e.g., TLR2. Other ligands and TLRs can also be used.

Example 8 TLR2 Binds to PorinB in Cell-Free Systems

The binding of TLR2 ligands was assessed by ELISA in a cell free system.

Briefly, various TLR2 ligands were plated on plastic in carbonate bufferpH 9 for two hours at different concentrations (X axis) in duplicatepoints. After washing (PBS-0.05% Tween 20), a fusion protein consistingof the extracellular domain of TLR2 and the mouse Fc portion ofimmunoglobulin G, isotype 2a (TLR2:Fc, see U.S. Provisional PatentApplication Ser. No. 60/598,774), was added at 1 mg/ml (0.1 mg/well).After extensive washing, the bound TLR2:Fc protein was revealed byincubation with a HRP conjugated anti mouse polyclonal antiserum and theELISA developed using standard chromogenic substrates for the enzymeHRP.

The results, shown in FIG. 8A, demonstrate that this assay can be usedto determine binding of various ligands to TLRs in vitro.

In a similar setting, the TLR2:Fc fusion protein and the relatedTLR4:Fc, were plated on plastic and the biotinylated ligand used toprobe the wells. The TLR2 bound biotinylated protein was reveled using aHRP conjugated anti biotin polyclonal antiserum (NEB).

The results are shown in FIG. 8B. TLR2 specifically bound tobiotinylated PorinB, whereas the TLR4 fusion protein did not.

Thus, these methods allow the screening of TLR2 interactors in amultiwell format, which can be easily handled by robotic liquidhandlers, providing for high-throughput assays.

Example 9 TLR4 Binds to LPS in Cell-Free Systems

TLR4 is the receptor responsible for activating cells in response tolipopolysaccharide (LPS) challenge. It is a typical TLR, in that it hasa LRR extracellular domain and an intracellular TIR. TLR4 can sense LPSonly when in the presence of MD-2, a secreted 160 amino acidglycoprotein that associates with the extracellular domain of TLR4. LPSis thought to interact with both TLR4 and MD-2. MD-2 is a stand aloneLPS receptor, as it can bind to LPS without TLR4. However, TLR4 cannotinteract with LPS in the absence of MD-2 (Visintin et al., 2003, supra).

B1287 is a synthetic LPS analog developed by Eisai Research Institute(Andover, Mass.; see International Patent Application No.WO-9639411-A1); see Ingalls et al., 1998, J. Immunol., 161:5413-5420.This compound antagonizes the effects of LPS; as the mechanism is bypreventing the interaction of MD-2 and TLR4 with LPS.

Briefly, cells expressing a GFP tagged TLR4 chimeric protein wereincubated with fixed amounts of biotinylated LPS (1 mg/ml) andincreasing amounts of the LPS antagonist B1287 for one hour at theindicated concentrations. The results are shown in FIG. 9, top panel. At0 competitor (lane 1), the binding is maximal, and the avidin beadscould precipitate biotinylated LPS and the associated TLR4^(GFP)molecule, as revealed by western blotting for GFP. However, B1287 couldefficiently prevent the interaction of TLR4 and LPS, thus preventing theformation of a precipitable complex containing TLR4, in a dose dependentmanner. At a concentration roughly 10 fold the LPS (in weight), thecompetitor could completely block the interaction. This method can beused to screen for LPS antagonists/agonists (TLR4 interactors) in livingcells.

In a parallel experiment (FIG. 9, lower panel), supernatants from thesame cells in A were precipitated using streptavidin beads and thepresence of LPS bound MD-2 was assessed in the pellets by anti FLAGwestern blotting. As expected, the LPS antagonist B1287 couldefficiently prevent the interaction of LPS with MD-2 as well.

Other Embodiments

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

1. A method of identifying a compound that modulates Toll-like receptor(TLR) signaling, the method comprising: (a) providing a samplecomprising a TLR polypeptide; (b) contacting the sample with a cognateTLR ligand and a test compound, thereby forming a test sample; (c)incubating the test sample for a time and under conditions sufficientfor the TLR ligand to bind to the TLR polypeptide in the absence of thetest compound; and (d) determining binding between the TLR polypeptideand the TLR ligand in the test sample, wherein a difference in bindingin the test sample compared to a control indicates that the testcompound is a candidate compound for modulating TLR signaling.
 2. Themethod of claim 1, wherein the TLR ligand or the TLR polypeptide isbiotinylated.
 3. The method of claim 1, wherein the TLR polypeptide is achimeric polypeptide comprising a TLR protein or fragment thereof, and asecond protein.
 4. The method of claim 3, wherein the second proteincomprises a fluorescent protein.
 5. The method of claim 4, wherein thefluorescent protein is Green fluorescent protein (GFP) or a fluorescentvariant thereof.
 6. The method of claim 5, wherein the second proteincomprises an Fc fragment.
 7. The method of claim 1, wherein the TLRligand is bound to a solid surface.
 8. The method of claim 7, whereinthe TLR ligand is biotinylated and the solid surface comprises avidin,streptavidin, or a deglycosylated form of avidin.
 9. The method of claim1, wherein the TLR polypeptide is bound to a solid surface.
 10. Themethod of claim 9, wherein the TLR polypeptide is biotinylated and thesolid surface comprises avidin, streptavidin, or a deglycosylated formof avidin.
 11. The method of claim 1, wherein one or more of the TLRpolypeptide and the TLR ligand is labeled.
 12. The method of claim 11,wherein the label comprises europium or allophycocyanin
 13. The methodof claim 1, wherein the binding between the TLR polypeptide and TLRligand is detected by time resolved fluorimetry.
 14. The method of claim1, wherein the binding between the TLR polypeptide and the TLR ligand isdetected with an antibody that specifically binds to the TLRpolypeptide.
 15. The method of claim 14, wherein the antibody is labeledwith a lanthanide chelate fluorophore and time-resolved fluorimetry isused to detect the binding.
 16. The method of claim 14, the TLRpolypeptide is a chimeric TLR polypeptide, and the antibody binds to thesecond protein in the chimeric polypeptide.
 17. The method of claim 1,wherein the TLR polypeptide and TLR ligand are in solution.
 18. Themethod of claim 1, wherein the particle comprises a bead.
 19. The methodof claim 1, wherein the TLR polypeptide is a TLR9 polypeptide or a TLR2polypeptide.
 20. The method of claim, wherein the difference in bindingis one or more of a difference in a rate of binding; a rate ofdissociation; a difference in an amount of binding; or a difference inan affinity of binding.
 21. The method of claim 1, further comprising:(a) administering a compound that modulates Toll-like receptor (TLR)signaling to an animal model of a disorder associated with TLRsignalling; and (b) evaluating an effect of the compound on a parameterof the disorder in the animal, (c) wherein a positive effect of thecompound indicates that the compound is a candidate therapeutic compoundfor the treatment of the disorder.
 22. The method of claim 21, furthercomprising optimizing the compound.
 23. The method of claim 21, furthercomprising formulating a therapeutic composition comprising a candidatetherapeutic compound and a pharmaceutically acceptable carrier.